Thermo-electric couple.



PATENTED JULY 5, 1904.

W. H. BRISTOL.

THERMO ELECTRIC COUPLE.-

APPLIOATION FILED APB.. 4, 1904.

N0 MODEL.

Flai

/NVENTO/.' 'Z uw Mmm VBY l//r n ynuire-1,176.

.Unitas Sanitas Patented July 5, 1904.

PATENT OFFICE'.

Trissino-amrique COUPLE.

SPECIFICATION forming mit of Letters; Patent No. 7e4,176, A'elated July 5, 1904.

' Applicata); fi1eaApri14,19o4. seriali 110.201.580. (N o moana for indicatingor measuring the temperatures of baths-such, for instance,- as moltenjlead,

I copper, tin, aluminium,&c.-used in the arts for various purposes, aswell as for measuring the temperatures of mercury or like meleach other generally by electric welding to form a junction. The ends of the elements soon become brittle, corroded, or ama'igamated with repeated or continued use,4 and `consequentlythe readings of the instrument.

are unreliable. Itis diiiicult to replace the junction orto repair the same, and new elements must generally be substituted. vAccordingto my invention l do not directly connect the terminals or. ends .of the elements comprising the couple, but leave the same in` a separated condition and cause their junction to be virtually effected by a liquid metallic bath into which the terminals are introduced, or accomplish the sameresult by making use of` the receptacle as oneelement of thecou- `ple'or form the entire or a part of one ele-v ment by the articlewhich is to be subjected to the temperature desired in the bath. Itv

will readily be understood that if the terminais become corroded,'amalgamated, &c. they can be easily ground do'wn or replaced ones' with very littleexpense.

My invention therefore consists, essentially,

new

in athermo-electric couple -conilprising two separated elements, a lquidbath into which said velements extend, and means in connection with said elements for measuring the difhas reference vto 'improvei ference of temperatures at opposite ends -thereof by means-of the variation of electromotive force due to the difference of temperature at opposite ends of the dissimilar metals forming the couple;A

the accompanying draw-ings, in which.-v

. Figure 1 represents an elevation, partly 1n section, showing diagrammatically one form 'of pyrometer embodying my invention. Fig.

l shows the elements held to each other by an insulating ImateraI. Fig. 2 is a similar View showing a modified form in which the i receptacle forms one of the elements 'of the couple. Y Fig. 3 is a similar view showing the article to be treated connected directly with and forming part of one of the elements. Fig. Li-is a similar view showing a modified manvner of arranging the elements". Fig 5 isa designate corresponding parts throughout the several views of the drawings.

The nature of my'invention will best be un`. derstood when described in connectionwith"v y Referringto Fig. 1 of the dra-wings, the# letters A and. B designate the elements of a thermo-electric couple, the terminals L and I) of which are left 'separated one from the other Ainstead of being joined together, las usual.

C is a receptacle which may be in the form of a pot or crucible ,or may be the hearth of a furnace into which the elements A and B are placed'and, if desired, maintainedf'in a defi- .nite or adjustable position by means ofasuitis an. electrical indicating or recording instrumentj-'fsuch, 'for instance, as a voltmeter of any suitable construction-to the bindingwires 10J and 11. Itwill'readily be understoodv that when the ends 'of the elements A. f and B are immersedin the bath contained in .the receptacle C the liquid or molten metal l in itself acts as a junction orbridge; for the ltwo terminals and a current is established'v in the same manner as if the elements were directly joined, theyelectromotive force delposts of which the elements are connected by pending on the difference in temperature between the two opposite ends or terminals of the elements. The elements may bejsimply separated, as shown in Fig. 1, or they may be l held to each other byan insulating material A `the same material as the receptacle to the receptacle. This construction is shown in Fig.

2. Again, the article to be heated may be atpair of tongs adapted tached to one of the elements and practically form part of the same incoperation with the other element. A construction of this character. I have illustrated in Fig. 3,v where P designates the article to' be immersed in the bath-say, for instance, a steel drill-and-Ai` is one of the elements which is provided with-l means for attaching the article-such,vfo rin' stance, as a socket and screw 3. Of course a to hold.the .,article and placed in electrical connection with the indicating or measuring instrument can be used to the sameend. As the character or nature of the s teel or other metal varies with different lots, I find it practicable to employ-means for changing the' resistancein the circuit according to the varying.conditions. The va. riable resistance R interpolated in thecircuit enables an instrument having a single scale or chart to be used with different metals form'- ing the elements. Byproperly adjusting the resistance when the elements are placed into a bath, which is just at its melting or fusing point, until the indicating-hand givesa reading corresponding to the known meltingpoint of the bath, the instrument willbe correct at this temperature.- In case of elements such, for instance, as vnickel and vsteel slight variations in different lots would not seriously over the whole range.

affect the remaining readings of the instrument. The variable resistance also permits an instrument with a scale to be readily adjusted by varying the resistance so-that the indications will correspond to graduations The same arrangement (shown in Fig. 3) is applied in the 'com' mercial tinning or galvanizing of metallic plates. I

In Fig. 4 I have shown thecouple in convenientform ,for commercial use, one' of the elements, A, being in the form of a rod and the other, B, in thel forni of a tube,` the intervening annular space being filled with insulating material I, whichl should' be of a refractory nature whenl the instrument is to Y' used for.measurng`high temperatures.

exposed lto high temperatures becomes brittle or is burned out suilicientlyv to cause anappreciable error in the reading of the vinstrument, theparts so affected can be readily'removed by grinding-or otherwise, so as to present new surfaces to the bath. for reestablishing the connection through the medium of the liquid bath.

For pyrometers for measuring extremely ,high temperatures theconstruction shown inA Fig. 5 is very suitable. lIn this instance I make use of primary elements, asA and B, which are not joined excepting when bridged by the liquid Vbath and are made of materials,` such as platinum and platinum-alloy, capable of withstanding high temperatures, and com- 'bined' with the same are conductors, as Fand F', of' a cheapermaterial-say steel-not capable of resisting extremely. high temperatures and are not exposedito the extremely high temperatures. These additional conductors form secondary couples, neutralizing each other, as described in my prior application, Serial No. 196,440, filed March 5,1904, and need not be more fully described here.

Of course it is to be understood that the receptacle C of Fig. 3 could, similar to the receptacleC of, Fig.'2, be usedas one of the elements instead of employing the element B.

Since the electromotive force of the couple depends n the dii'erence'of temperature-at opposite ends of the elements, it is evident that in order to eleminate the effects of changes in the surrounding atmosphere at said outer ends suitable means for maintaining a constant temperature should be used. A water, steam, or other jacket, as J, of a usual con.- struction (indicated by dotted lines in Fig. 1) will answer this purpose and is-applicable to all the lothe'ri'orms here shown.

. r1. Athermo-electric couple comprising two separated elements, a liquid bath into which said elements extend, and means in connection with said elements for measuring the-difference-of temperature at opposite ends thereof by means of the variation of electromotive force due to the difference of temperature at opposite ends of the dissimilar metals forming the couple. v

2. A thermo-electric couple comprising two ,separated elements having separated hot terminals `or ends, a liquid bath into which said elements extend, and means in connectionwith lsaid elements for measuringthe difference of of the variation of electromotive 'force due to the difference of temperature at opposite ends of the dissimilar metals forming the couple.

3. The combination with a thermo-electric `couple comprising two separated elements, an electrical measuring instrument in connection with the hot or vcoldends of the elements, and

' When with continued or repeated use the end temperature at opposite ends thereof by means 1 a liquid bath connecting the opposite ends and said elements extend, means in connection with said elements for measuring the difference of temperature at opposite ends thereof by means ofthe variation of electromotive force due to the diii'erenee of temperature at opposite ends of the dissimilar metals forming the couple, and a variable resistance interposed in the circuit.

5. A thermo-electric couple comprising two separated elements, a liquid bath into which said elements extend, an insulation between the elements, and means in connection with said elements for measuring the difference of temperature at opposite ends thereof by means of the variation of electromotive force due to the difference of temperature at opposite ends of the dissimilar metals forming the couple.

6. A thermo-electric couple comprising a tubular element, a second element made in the form of a rod and passing into the first element,. and an intermediatel filling of insulating material, said elements being separated from each other, substantially as described 7. A thermo-electric couple comprising two separated elements, a liquid bath into which said elements extend, means in connection with said elements for measuring the difference of temperature at opposite ends thereof by means of the Variation of electromotivc force due to the difference of temperature at opposite ends of the dissimilar metals, and means for maintaining the temperature at the' outer ends of the elements substantially constant.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

WILLIAM H. BRISTOL. Witnesses:

RAENA H. YUDIZKY, A. FABER DU FAUR, Jr. 

